238 
present in the first chalimus (Fig. 20 h) . The 
appendage in this stage is a one-segmented lobe. 
The proximal end is broader than the rounded 
distal end, the lateral margins are wavy, and the 
distal surface bears three spinule-like processes. 
The fourth thoracic leg of the second chal- 
imus (Fig. 20/ ) is lobate and somewhat longer 
than the appendage of the preceding stage. An 
indistinct division is present in the middle of 
the appendage, dividing it into two segments. 
Whether it is right to call the proximal segment 
of the appendage the protopodite and the re- 
maining segments the exopodite as this author 
has previously done with regard to adult cali- 
gids (Lewis, in press) was not determined. For 
the present, however, because of the lack of 
definite information on this problem, the terms 
"protopodite” and "exopodite” will not be used 
but the segments simply referred to by number, 
with the proximalmost segment being the first. 
The proximal end of the first segment of the 
fourth thoracic leg of the second chalimus is 
broad and angled so that the appendage projects 
posteriorly and laterally from its junction with 
the fourth pedigerous segment. The second seg- 
ment bears three short, terminal, spinelike proc- 
esses. 
The fourth thoracic leg of the third chalimus 
(Fig. 20)) has lost its general lobate shape and 
is now three-segmented. The first segment is 
short, its greatest length approximately three- 
fourths of the width; the segment is tapered 
from the broad proximal to somewhat narrower 
distal end. The second segment is about twice 
the length of the first and almost twice as long 
TABLE 5 
Armature of Fourth Thoracic Legs of 
Developmental Stages* 
STAGE 
MARGIN 
1 
SEGMENTS 
2 3 
4 
Chalimus I 
outer 
3h 
Chalimus II 
outer 
3h 
Chalimus III 
outer 
lh,2H 
Chalimus IV 
outer 
lh,2H 
Chalimus V 
outer 
lp 
lh,lh,2H 
Chalimus VI 
outer 
IP 
Ih 
1H 
3H 
Adult 
outer 
Ip 
1H 
IH 
3H 
* For explanation of symbols see Fig. 1 . 
PACIFIC SCIENCE, VoL XVII, April 1963 
as broad; the lateral margins are irregular al- 
though basically parallel, and the distal and 
proximal margins are both irregular. The third 
segment is greater than one-half the length of 
the second, the lateral margins are flatly convex, 
and the distal margin is rounded and continuous 
with the inner lateral margin. Three spinelike 
processes are present on the distal surface of 
the third segment. 
The fourth thoracic leg of the fourth chalimus 
(Fig. 20k) is somewhat similar to the third 
chalimus appendage. The length and width of 
the entire appendage is slightly greater than that 
of the preceding stage, the first segment is com- 
paratively shorter and wider, the second seg- 
ment appears swollen, and the third segment is 
not as distinctly separated from the second. 
The fourth thoracic leg of the fifth chalimus 
(Fig. 20/) is three-segmented. The first seg- 
ment is ovoid, the lateral and distal margins 
broadly rounded and the outer distal lateral sur- 
face bearing a single plumose setule. The divi- 
sion between the second and third segments is 
indistinct in contrast to the distinct division 
present in the preceding stage. The combined 
lengths of the second and third segments is ap- 
proximately equal to that of the first segment. 
One poorly developed spine is present on the 
outer distal lateral surface and two well-devel- 
oped and one poorly developed spines are borne 
on the distal surface of the third segment. 
The fourth thoracic leg of the sixth chalimus 
(Fig. 20 m) is four-segmented. The first seg- 
ment is slightly longer than the combined 
lengths of the three distal segments, the proxi- 
mal and distal ends of the segment are slightly 
narrower than the middle of the segment, and 
the lateral margins are wavy. A single plumose 
setule is present on the outer distal lateral sur- 
face of the segment, as in the preceding stage. 
The second segment is short, its greatest length 
slightly less than that of the third segment; the 
lateral margins are flatly convex, the outer much 
longer than the inner. A short, simple spine is 
present on the outer distal corner of the second 
segment. The third segment is tapered from the 
proximal to slightly broader distal end; the lat- 
eral margins are flat or flatly convex, the outer 
longer than the inner. A single simple spine is 
present on the outer distal corner of the seg- 
ment. The fourth segment is slightly broader 
